Illumination systems where a lamp such as discharge lamps or incandescent lamps have been arranged in reflector adapted the reflect a part of the emitted light in a predefined direction along an optical axis have been known for many years. Further it is known that such lamps need to be cooled in order to provide stable emission spectra of the emitted light and improve the lifetime of the lamp.
Such illumination systems can be used in projecting systems where the light need to be coupled through an optical gate where a light modifying element such as gobos, LCD, DMD or DLPs can be positioned and where an optical system is adapted to image the optical gate at a target surface along the optical axis. Projecting systems are also widely used in the entertainment industry where the illumination devices are used to create exiting light effects and for instance can be mounted in a moving head light fixture. In a moving head light fixture the projecting system is arranged in a housing rotatable connected to a yoke, which is rotatable connected to a base. The head can hereby be panned and tilted in relation the base and the light beam created by the projecting system can thus be moved around.
In projecting systems it is known to arrange a retro reflector along the optical axis and which is adapted to reflect a part of the emitted light back to the reflector. Such retro reflector makes it possible to increase the intensity of the light coupled through the optical gate, as a part of the back reflected light will be reflected towards and through the optical gate by the main reflector. In other words the retro reflector makes it possible to couple the outermost part of the light beams through the optical gate.
U.S. Pat. No. 1,256,522 discloses an illumination system where an electric lamp is provided with a socket, which is positioned within a tubular sleeve arrange axially of a reflector casing. The reflector is formed as an elliptic reflector. A hemispherical retro reflector is detachably secured to the main reflector. The retro reflector has an opening aligned with the lamp and wherein a tubular shell is into which a lens casing is telescopically fitter for adjustment toward or away from the lamp. The lens casing comprises a number of lenses. Further an annular cooling chamber has been arranged around the tubular shell. The annular cooling chamber comprises an inlet tube connected to blowing means and cooling air is forced into the cooling chamber. A number of apertures have further been provided in the retro reflector and around the tubular shell and the cooling air it thus forced into the reflector chamber thought these apertures. At the bottom of the main reflector a number of corresponding apertures have been provided around the socked and the cooling air is thus exhausted out of the reflector chamber through theses apertures. The cooling air is thus capable of removing heat from the lamp part itself however the heated cooling air is blown towards the bottom part of the lamp and can as a consequence result in heating of the socket part of the lamp, which is not desired with discharge lamps. Another issue is the fact the lamp system of U.S. Pat. No. 1,256,522 are very expensive to manufacture as many parts need to be assembled and aligned correctly in order to work probably.
U.S. Pat. No. 7,018,076 discloses a high performance compound reflector and cooling system for use with a projection system having a lamp for emitting light, an ellipsoid reflector for capturing said light from a first focal point of the ellipsoid reflector and focusing said light at a second focal point co-incident with an integrator rod, and a spherical reflector for retro-reflecting light through the first focal point for reflection by said ellipsoid reflector to said second focal point. The shape of the ellipsoid reflector according to the present invention allows the spherical element to have a larger diameter at the interface between the ellipsoid and sphere. This provides a location for an air deflector in a shape similar to the back of the ellipsoid for channeling air over and outside of the ellipsoid and then along the inside of the sphere. The design of the reflector and air deflector allow cooling requirements to be substantially reduced. This system requires that the top part of the light source are positioned in the aperture of the retro reflector in order to allow the cooling air to cool the top part of the light source, which in many situations not possible. Further the cooling air will become heated as is flows across the outer part of the main reflector and as a consequence the cooling air will only be able to remove a limited amount of heat from the top part of the light source and will in many in situations even be heated so much that it actually provides heat to the upper part of the light source instead of removing heat.
Moving head lighting fixtures are commonly known in the art of lighting and especially entertainment lighting. A moving head light fixture typically comprises a head having a number of light sources which creates a light beam and number of light effect means adapted to create various light effects. The head is rotatable connected to a yoke and the yoke is rotatable connected to a base and the result is that the head can rotate and direct the light beam in many directions.
The competition in the market has traditionally been based on the optical performance of the moving head such as light output, number of light effects, color mixing etc. The competition in the market has lately changed such that parameters such as quality, serviceability and price have become the most important factors. There is thus a need for a competitive moving head lighting fixture with regard to quality, serviceability and price.